Sony TC K7II (around 1977)
A stereo cassette deck with a precision tape transport, advanced for its time.
Overview
The Sony TC-K7II is a stereo cassette deck from the late 1970s, built on Sony's electronics know-how. The design is aimed at stable tape transport and high-fidelity playback. Two cosmetic variants were made: the silver TC-K7II and the metallic-colored TC-K7BII. The deck handles 4-track 2-channel stereo recording and playback. A 3-position bias and equalizer selector covers Normal, CrO2, and Fe-Cr tapes.
Specifications
| Track system | 4-track 2-channel stereo |
| Bias frequency | 105kHz |
| Fast-forward and rewind time | Approximately 70 seconds (at C-60) |
| Total S/N | 60 dB (Fe-Cr, peak level, Dolby NR off) |
| Total S/N | 56 dB (CrO2, peak level, Dolby NR off) |
| Dolby NR on improvement | 5 dB improvement (at 1 kHz), 10 dB improvement (5 kHz or more) |
| Overall strain rate | 1.3% |
| Frequency characteristic (Dolby NR off) | 20 Hz ~ 18kHz/30Hz ~ 16 kHz ± 3 dB (Fe-Cr) |
| Frequency characteristic (Dolby NR off) | 20 Hz ~ 17.7kHz/30Hz ~ 15 kHz ± 3 dB (CrO2) |
| Wow and flutter | 0.045%(WRMS) |
| Input terminal Mic | 0.2 mV (-72dB) / for Low Impedance Microphone |
| Input terminal Line | 0.06 V (-22dB) / 100k Ω |
| Output terminal Line | 0.775 V (at 0 dB, 100k Ω load) |
| Output terminal Headphone | 8 Ω ~ 32 Ω |
| Remote control jack | 11-pin connector |
| Semiconductor used | Transistor : 94, Diode : 69, FET : 1, LED : 3, IC : 2 |
| Power outlet | Unswitched : 1 system, 300W |
| Power | 100 VAC, 50Hz/60Hz |
| Power consumption | 26W |
| External dimensions | Width 430 x Height 170 x Depth 310 mm |
| Weight | 10kg |
| TC-K7II price | ¥ 99,800 (around 1977) |
| TC-K7BII price | ¥ 105,000 (around 1977) |
Design
The capstan is driven by a green FG-type servo motor. Sony chose it for durability, low noise, and stable rotation. A 90 mm dynamically balanced flywheel helps keep the transport steady. The recording/playback head is an F&F (Ferrite & Ferrite) type, coupled directly to the amplifier so there are no coupling capacitors to degrade the sound. A dedicated IC-based logic circuit allows direct mode changes (e.g., STOP to PLAY) without mechanical stress. The peak level meter is a 3-step LED type (0 / +4 / +8 dB) for accurate transient response. The deck also has Dolby B noise reduction, an MPX filter to block 19 kHz FM pilot interference, and a Sony-designed limiter circuit. The Memory Stop/Play function supports recording, playback, and repeat operations. Line and microphone inputs can be mixed, and the front panel line-in takes priority. Line output and headphone output each have their own volume control. There is also a Record Mute function and auto shut-off. Holding FWD while pressing REC gives quick follow-up recording. A wired remote (RM-30) and a program timer, both sold separately, enable timed recording and alarm playback.
Context
Sony developed this stereo cassette deck with its know-how and the latest electronics technology of the time.
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